Effects Of Reclaimed Water Irrigation On Soil Quality In The Slope

The utilization of mine water is a shortcut to solve the problem of water shortage in mining area.The reclaimed water of mine is reused in production,life and ecology,which improves the utilization efficiency of water resources,but also causes a series of soil environmental problems.This phenomenon has attracted more and more attention.To reveal more details of this aspect,a research experiment was conducted on effects of reclaimed water irrigation on soil quality of the slope in buertai mine of Shendong mining area.There are25 soil attributes in the 0-20 cm,20-40 cm and 40-60 cm soil layers belonging to two sites that are irrigation site（under reclaimed water of mine）and non-irrigation site（under natural conditions）in the slope,including soil salinity-sodicity indices(EC,p H,SAR,Na⁺,K⁺,Ca²⁺,Mg²⁺,HCO₃^-,Cl^-and SO₄^2-),fertilizer indices（SOM,TN,TP,TK,AN,AP and AK）and heavy metals（As,Cd,Cr,Cu,Hg,Ni,Pb and Zn）.This research analyzed the effects of soil salinization,nutrients and heavy metals under irrigation water and evaluation soil quality status by soil quality index（SQI）.Results can provide a theoretical basis for the promotion and safe use of mine reclaimed water irrigation.The main conclusions are as follows:From the perspective of irrigation water quality,TDS(1227.80 mg·L^-1),Cl^-（352.72 mg·L-1）and SO₄^2-（351.38 mg·L-1）of the water in Bultai mining area slightly exceed Chinese standards for irrigation water quality（GB5084-2021）and Chinese standards for groundwater quality(GB/T14848-2017.The combination of SAR,Na%and RSC showed they were within the allowable limit（SAR<10,Na%<60,RSC<1.25）,but the values of EC was 2190～2510μs·cm^-1,slightly higher than the threshold（750μs/cm<EC≤2250μs/cm）.This indicates that the use of mine reclaimed water for ecological irrigation in the study area might cause the risk of soil salinity.Reclaimed water irrigation has a certain impact on salinity of soil in the slope.After reclaimed water irrigation,soil EC,Na⁺and SO₄^2-increased significantly in the 20-40 cm and 40-60 cm soil layers（P<0.05）,Ca²⁺was leached in each soil layers of the slope.Mg²⁺,K⁺,Cl^-and HCO₃^-migrated and accumulated in the lower soil layer under the irrigation water,compared with the non-irrigated area,which increased by 88.29%,37.50%,47.06%and7.83%in the 40-60 cm soil layer,respectively.With the Reclaimed water irrigation,p H and SAR values had no significant change.Soil fertilizer and soil comprehensive fertility quality had increased under reclaimed water irrigation.SOM and available nutrients increased by15.32%～1051.49%and 0.22%～127.92%respectively,TN increased by1.38%～65.67%,TP and TK increased by 4.21%～26.26%respectively.Soil comprehensive fertility quality was calculated by Nemoro quality index,showing that soil fertility quality in irrigated site was increased by 7.16%～52.18%.Heavy metal elements in the soil concentrated on the upslope and middle slope of different soil layers under reclaimed water irrigation.Cd significantly accumulated in the soil layers,which belongs to the level of moderate pollution and the risk level of moderate ecological pollution.In addition,the pollution degree of the upper and middle slopes was higher,and showed a decreasing trend from the top to the bottom of the slope.The results of soil quality index（SQI）showed that the values of SQI in the 20-40 cm and 40-60 cm soil layers in the upper and middle slopes of the irrigated area was significantly higher than that in the non-irrigated area,increasing by 11.11%-26.67%and 16.78%-41.88%,respectively.Reclaimed water irrigation improved the soil quality on the upper and middle slope,and the increase of SQI in the deep soil was greater.